Field of the Invention
The present invention relates to a steam or inert gas injection gas turbine for injecting steam or inert gas to a combustor and a control method therefor and more particularly to an operation method of a gas turbine compressor.
Description of Related Art
In high-efficiency realization and high-output realization of a power generation gas turbine, the combustion temperature of the combustor needs realization of high temperature, however, in correspondence with a rise of the combustion temperature, the generation rate of NOx increases exponentially. NOx is generated in a portion locally raised in temperature by a diffusion flame, so that a method of injecting steam into the combustor, thereby lowering the combustion temperature of the high-temperature portion in the combustor, and reducing NOx is widely used. Further, steam is injected into the combustor, thus the combustion temperature in the combustor falls, so that it is possible to input more fuel and increase the gas turbine output.
As mentioned above, steam is injected into the gas turbine combustor, thus the effects of reduction in NOx of exhaust gas of the gas turbine and improvement of the gas turbine output are obtained, however, high-pressure steam is injected into the combustor, thus the pressure ratio of the gas turbine compressor increases and the axial flow speed decreases. Therefore, the reduction in the compressor reliability becomes a problem such that the pressure ratio per each vane stage of the compressor increases and the vane load of the compressor increases, thus there is a risk that an unstable phenomenon such as surging may be caused.
Further, in the gas turbine with steam or inert gas injected, the pressure ratio is changed due to the change in the ambient environment temperature. For example, at the time of a low temperature, the atmospheric density is higher than that at the time of a high temperature, so that the mass flow rate in the compressor increases and the pressure ratio increases compared with at the time of a high temperature. Therefore, similarly, the reduction in the compressor reliability comes into a problem.
In the axial flow compressor of the gas turbine, generally, as an air flow rate adjustment mechanism of the compressor, an inlet guide vane is attached. The inlet guide vane is a vane(s) capable of actively controlling the vane attaching angle in a stator vane at one stage or stator vanes at a plurality of stages close to the inlet of the compressor, and the angle of the inlet guide vane(s) is adjusted, thus the flow rate and pressure ratio in the compressor can be adjusted. By the adjustment of the inlet guide vane(s), when the flow rate of the compressor is reduced, the pressure ratio is reduced, then the axial flow speed in the compressor is reduced. Therefore, depending on the stage of the compressor, the vane load increases and a risk of generation of an unstable phenomenon such as surging may be increased.
As mentioned above, in the gas turbine with the combustor injected with steam, under the conditions of the atmospheric temperature, if the inlet guide vane opening and the steam injection rate are not appropriate, there is a risk of an extreme reduction in the compressor reliability. As a method for controlling the guide vane opening for the steam injection rate, in the patent literature 1, a method for opening and closing the guide vane opening in accordance with an increase and a decrease in the steam injection rate so as to keep the pressure ratio constant is described. Further, in the patent literature 2, to ensure the compressor vane reliability in correspondence with the atmospheric temperature and atmospheric humidity, a method for restricting the guide vane opening is described.